Gasification of a solid carbonaceous fuel is obtained by the reaction of the fuel with oxygen. The fuel mainly contains carbon and hydrogen as combustible components. The gas-carried finely divided carbonaceous fuel and the oxygen-containing gas are passed via the separate channels in the burner into a reactor at relatively high velocity. In the reactor a flame is maintained in which the fuel reacts with the oxygen in the oxygen-containing gas at temperatures above 1300° C. to form mainly carbon monoxide and hydrogen.
Various burner designs have been proposed in the prior art. EP-A-328794 describes a burner wherein finely divided coal is supplied to a burner front via a central channel disposed along the longitudinal axis of the burner, and oxygen-containing gas is supplied via at least one annular channel surrounding said central channel. The oxygen is directed into the flow of coal at the burner front.
EP-A-130630 describes a burner wherein at the burner front, an oxygen containing gas is discharged from a central channel at high velocity and an oxygen containing gas is discharged from an annular outlet at a lower velocity. A solid fuel is discharged from a number of outflow openings located between said central and annular oxygen outlet openings. According to this publication, the outer low velocity oxygen stream serves to protect the burner against overheating due to suction of hot gasses. The publication discloses that if the burner is used for large throughputs, the outlet openings for the solid fuel are preferably not of an annular shape. It is stated that such a design would not result in a proper contact of all the solid fuel particles with oxygen.
The burner type according to EP-A-328794 has been used commercially with great success. However, at high throughputs the heat-flux to the burner front increases to such values that burner lifetimes may become too short.
EP-A-130630 addresses the issue of heat flux to the burner front by applying a low velocity oxygen shield around the flame. A disadvantage of the burner according to EP-A-130630 is that for high throughputs, the solid fuel is passed through separate channels to the burner front, which may cause erosion problems. Another problem is the complexity of the design due to the fact that one metal piece with multiple channels for solid fuel and oxygen containing gas needs to be manufactured.